One example of a process for manufacturing a semiconductor includes a film formation process of depositing a predetermined thin film on a substrate using a chemical vapor deposition (CVD) method or an atomic layer deposition (ALD) method. The CVD method refers to a method in which a thin film having elements included in a source molecule thereof is deposited on a substrate to be treated using reaction of a vapor phase of a gaseous source and a surface of the substrate. Among CVD methods, controlling the deposition of a thin film at an atomic layer level is referred to as an ALD method, and the ALD method is characterized in that a temperature of the substrate is low. Also, plasma is used to remove impurities from the thin film deposited using the CVD method or aid in performing a chemical reaction of a film forming source adsorbed using the ALD method.
For example, formation of an amorphous silicon nitride film (hereinafter referred to as a “SiN film”) using the ALD method is performed using dichlorosilane (DCS) and ammonia (NH3) plasma. A process of forming a SiN film on a substrate includes, for example, DCS irradiation treatment and NH3 plasma irradiation treatment. Both of these treatments are repeatedly performed (hereinafter referred to as “cycle treatment”) to deposit a SiN film having a predetermined film thickness on a substrate.
In such an ALD or CVD method, however, a thin film is cumulatively deposited on a contact portion in addition to the substrate. Foreign substance contamination in which microcracks are generated due to the cumulative deposition and the substrate is contaminated by foreign substances formed by peeling of the microcracks is problematic. The foreign substance contamination readily takes place as a deposition rate and a thickness of a cumulative film increase.
To prevent the foreign substance contamination as described above, a cleaning process for removing a cumulative film by performing cleaning treatment after a series of film formation treatments is also executed. Such treatment includes introducing a cleaning gas such as nitrogen trifluoride (NF3) or fluorine (F2) into a reaction chamber, reacting the cleaning gas with a SiN film, converting the SiN film into gases and exhausting the gases (for example, see Japanese Patent Laid-open Publication No.: 2009-33121).